NASHVILLE, Tenn. -- Opryland's 1,500 guests were spending the night in a high school to escape rising floodwaters that threatened other areas of downtown hit by devastating thunderstorms that slammed Tennessee and northern Mississippi, killing at least 19 people.

Authorities in Tennessee were preparing for more deaths and for the Cumberland River, which winds through the Music City, to crest at 10 feet above flood stage before sunrise, putting portions of downtown in danger of the kind of damage experienced by thousands of residents whose homes were swamped by flash floods.

The Cumberland River had already reached record levels since an early 1960s flood control project was put in place. With so much water inundating the Cumberland's tributaries, however, it was difficult to gauge whether the river would stop at 50 feet or exceed the forecast, increasing the water's spread in the city.

Authorities weren't taking any chances. They evacuated the downtown area, north Nashville where a leaky levee threatened residents and businesses. Flooding could hit the downtown tourism industry, the train depot and near LP Field, where the Tennessee Titans play.

"It's a lot like weather forecasting in that it's not exact," National Weather Service meteorologist Darrell Massie said of the prediction. "There's a lot of science behind it, but we still have to accept a certain amount of error."

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Forecasters were on the money when they warned residents there would be severe weather across the Mid-South, but few could have predicted the devastation the relentless line of storms brought.

Tennessee Gov. Phil Bredesen called it an "unprecedented rain event," but that failed to capture the magnitude. More than 13 inches of rain fell in Nashville over two days, nearly doubling the previous record of 6.68 inches that fell in the wake of Hurricane Fredrick in 1979.

"That is an astonishing amount of rain in a 24- or 36-hour period," Bredesen said Sunday.

At least 11 were dead in Tennessee and four in northern Mississippi. Tennessee Emergency Management Agency officials say there is likely a 12th victim, but a body had not been recovered. The death toll from storms in Arkansas, Mississippi and Tennessee since April 24 rose to at least 26 with several people missing. Three people in Mississippi were killed when high winds believed to be tornados hit their homes and a fourth died after he drove into flood waters.

The weekend deaths came on the heels of a tornado in Arkansas that killed a woman and injured about two dozen people Friday. And just a week ago, 10 people were killed by a tornado from a separate storm in western Mississippi.

Five people have died in Nashville where on Sunday authorities found two people who drowned in a home and two others who died when their vehicle overturned in flood waters.

Bredesen said officials hoped for the best, but knew there might be more deaths reported Monday as authorities got their first real look at the damage after a weekend filled with frantic rescues.

"This is going to go on for a while," Bredesen said. "It's going to take a while for the water to recede and us to get down into this. It's going to take several days for this to get back to anything near normal."

Much of the damage from flooding was done in outlying areas of Music City and across the middle and western parts of Tennessee. Rescues turned dramatic with homeowners plucked off roofs and pregnant women airlifted off a waterlogged interstate.

Firefighters busted through the windows of Audrey Talley's trailer early Sunday to rescue her family, including her three small grandchildren, ages 9 months to 4 years old. Talley's son woke her to tell her water was coming into the south Nashville residence. Within 10 minutes it was knee deep.

"We've lost everything," the 47-year-old Talley said at an emergency shelter at Lipscomb University. "I don't know what we're going to do. We've got nowhere to go."

The rain will end Monday but there will likely be weeks of cleanup for residents and public works employees alike. Though there was no official estimate, it was clear thousands of homes had been damaged or destroyed by flooding and tornados. Thousands of residents were displaced with some going to more than 20 shelters opened around Tennessee.

Hospitals, schools and state buildings also were flooded. Most schools in middle Tennessee would be closed Monday and most universities in the Nashville area postponed final exams, though many state workers were expected to return to their jobs, if possible.

The state's roads were in bad shape. The three major interstates in the Nashville area were closed over the weekend and Interstate 40, which runs east to west through the state, would likely remain closed since standing water is still stranding drivers.

Bredesen said more than 150 roads were closed in middle Tennessee alone with washouts and bridge damage destruction fairly common.

The Cumberland could add millions of dollars to the damage total.

While there aren't many residents in the area, downtown Nashville is home to a bustling tourist industry and financial center, a train depot and LP Field where the Tennessee Titans play. An increase to 52 feet -- 2 feet above the predicted crest and well above the previous record of 47.6 feet -- would greatly expand the damage.

Flooding and damage was so widespread in Tennessee that Bredesen asked the state's Army National Guard to help and dozens of vehicles and personnel were put to work rescuing stranded residents. Nashville Mayor Karl Dean reported more than 1,000 water rescues in the city alone, including that of a policeman who became trapped and clung to a tree for an hour before firefighters plucked him from the flood waters.

One building in east Nashville was caught on video Saturday floating down Interstate 24 and passing stranded vehicles. The video was quickly uploaded to YouTube.

Officials in Tennessee said Sunday the flooding is as bad as they've seen since 1975 when water memorably inundated the old Opryland amusement park east of downtown Nashville. Even the state's own emergency operations center wasn't immune. It took up to a foot of water below a false floor, forcing officials to relocate to an auxiliary command center.

"I've never seen it this high," said emergency official Donnie Smith, who's lived in Nashville 45 years. "I'm sure that it's rained this hard at one time, but never for this much of an extended period."